This invention relates to suspension apparatus for a motor vehicle and particularly to such a suspension having variable damping capability. The apparatus uses electrical damping by converting the vertical motion between sprung and unsprung masses into rotational motion in a multiphase alternator to generate an electric current in series with a variable electric load. As the current through the load is varied in response to a control signal, so is the damping of the suspension apparatus.
Electrical damping apparatus is not new in the broad sense. The U.S. Pat. No. 3,559,027 to Arsem, issued Jan. 26, 1971, shows a shock absorber for a motor vehicle which converts the linear suspension travel into rotary motion to activate a rotary electric generator, the output of which may be provided to a resistive load which may be varied to control the damping force of the apparatus. However, this prior publication does not show any control apparatus for varying the damping as the vehicle is operated and particularly does not show any recognition that the electrical apparatus may, if correctly designed, serve as the source of measurable vehicle suspensions parameters for inputs to such a control which eliminates the need for additional sensors. Other patents showing electrical shock absorbers, such as Starbard U.S. Pat. No. 3,981,204, issued Sept. 21, 1976, Schenevar U.S. Pat. No. 4,032,829 issued June 28, 1977, Gill U.S. Pat. No. 3,861,487, issued Jan. 21, 1975, and Lewus U.S. Pat. No. 3,921,746, issued Nov. 25, 1975, disclose the same or less. They, like Arsem, are primarily concerned with the generation of auxiliary power from such suspension movements for energy saving and only incidentally, if at all, mention the damping produced in the operation of the systems.